Volume 12, Issue 2 Ver. III (Mar - Apr. 2015)

1. IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE)
e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 12, Issue 2 Ver. III (Mar - Apr. 2015), PP 44-50
www.iosrjournals.org
DOI: 10.9790/1684-12234450 www.iosrjournals.org 44 | Page
Hydrogen Powered Vehicles- An Overview
Ankit Maroli, Ashish Kumar Khandual, Ashutosh Mahajani, Lohit Mahadevan
(Mechanical, Bharati Vidyapeeth College of Engineering/Mumbai University, India)
Abstract: Every day we come across headlines stating the increase in the usage of petroleum, diesel, or the
drastic changes in the weather due to Global warming. Because of this very reason mankind has started looking
for alternative fuels and energy sources. Strenuous efforts have been made over the past few decades finding if
the simplest element i.e. Hydrogen can actually deliver, serve the purpose of an alternative fuel and reduce our
reliance on oil. Is Hydrogen capable of replacing conventional fuels like gasoline/diesel?
Our paper highlights the important aspects of hydrogen powered vehicles, their types, and imprints a notion of
being in a pollution free state with negligible tailpipe emissions as well as shows the hindering pitfall of its
usage.
Keywords: Automobiles, Emissions, Hydrogen, Hydrogen Powered Vehicles, Weather Changes.
I. Introduction
Engine displacement, power output, fuel economy etc. have always been the most common factors when
it comes to gauging a car for its “on-road” capabilities. But in the last few decades, “emissions”, a previously
overlooked factor has become vital to building and buying “road-optimum” civilian automobiles. Car
manufacturers across the world face a serious deadline to reduce the tailpipe emissions of their automobiles.
This has led to an array of alternative fuels being discovered and researched upon. The standout amongst
these is Hydrogen. The vehicles derive their energy from the simplest element found on earth i.e. Hydrogen. The
truly fascinating feature flaunted by these fuel cells is “ZERO HARMFUL EMISSIONS”. Moreover the only
emissions are water vapor and heat.
II. Hydrogen as an Alternative Source of Energy
Hydrogen is the first element on the periodic table, making it the lightest element. Since hydrogen gas
is so light, it rises in the atmosphere and is therefore rarely found in its pure form, H2. In a flame of pure
hydrogen gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and releases
energy. The energy released enables hydrogen to act as a fuel. Since there is very little free hydrogen gas,
hydrogen is in practice only as an energy carrier, like electricity, not an energy resource. Thus, hydrogen gas
must be produced separately. Therefore, we need to have an insight on its properties and production and storage
in order to show its viability.
III. Characteristics of Hydrogen
There are several important characteristics of hydrogen that greatly influence the technological
development of hydrogen ICE and FCVs. [1]
Wide Range of Flammability: Compared to nearly all other fuels, hydrogen has a wide
flammability range (4-74% versus 1.4-7.6% volume in air for gasoline). This first leads to obvious concerns
over the safe handling of hydrogen. But, it also implies that a wide range of fuel-air mixtures, including a lean
mix of fuel to air, or, in other words, a fuel-air mix in which the amount of fuel is less than the stoichiometric, or
chemically ideal, amount. Running an engine on a lean mix generally allows for greater fuel economy due to a
more complete combustion of the fuel. In addition, it also allows for a lower combustion temperature, lowering
emissions of criteria pollutants such as nitrous oxides (NOX).
Low Ignition Energy: The amount of energy needed to ignite hydrogen is on the order of a magnitude
lower than that needed to ignite gasoline (0.02 MJ for hydrogen versus 0.2 MJ for gasoline). On the upside, this
ensures ignition of lean mixtures and allows for prompt ignition. On the downside, it implies that there is the
danger of hot gases or hot spots on the cylinder igniting the fuel, leading to issues with premature ignition and
flashback (i.e., ignition after the vehicle is turned off).
Small Quenching Distance: Hydrogen has a small quenching distance (0.6mm for hydrogen versus
2.0mm for gasoline), which refers to the distance from the internal cylinder wall where the combustion flame
extinguishes. This implies that it is more difficult to quench a hydrogen flame than the flame of most other fuels,
which can increase backfire (i.e., ignition of the engine’s exhaust).
High Flame Speed: Hydrogen burns with a high flame speed, allowing for hydrogen engines to more
closely approach the thermodynamically ideal engine cycle (most efficient fuel power ratio) when the

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stoichiometric fuel mix is used. However, when the engine is running lean to improve fuel economy, flame
speed slows significantly.
High Diffusivity: Hydrogen disperses quickly into air, allowing for a more uniform fuel air mixture,
and a decreased likelihood of major safety issues from hydrogen leaks.
Low Density: The most important implication of hydrogen’s low density is that without significant
compression or conversion of hydrogen to a liquid, a very large volume may be necessary to store enough
hydrogen to provide an adequate driving range. Low density also implies that the fuel-air mixture has low
energy density, which tends to reduce the power output of the engine. Thus when a hydrogen engine is run lean,
issues with inadequate power may arise.
IV. Hydrogen Production
Hydrogen can be produced from a variety of feedstock. These include fossil resources, such as natural gas and
coal, as well as renewable resources, such as biomass and water with input from renewable energy sources (e.g.
sunlight, wind, wave or hydro-power). A variety of process technologies can be used, including chemical,
biological, electrolytic, photolytic and thermo-chemical. Each technology is in a different stage of development,
and each offers unique opportunities, benefits and challenges. Two of the methods of producing Hydrogen are
explained below.
4.1 Methane Steam Reformer Plant
Steam reforming is a method for production of hydrogen, carbon monoxide or other useful products
from hydrocarbon fuels such as natural gas. This is achieved in a processing device called as a reformer which
reacts steam at high temperatures with fossil fuel. The steam methane reformer is widely used in industry to make
hydrogen.
Steam reforming of natural gas - sometimes referred to as steam methane reforming (SMR) – is the most
common method of producing commercial bulk hydrogen. Hydrogen is used in the industrial synthesis of
ammonia and other chemicals. At high temperatures (700 – 1100 °C) and in presence of a metal-based catalyst
(nickel), steam reacts with methane to yield carbon monoxide and hydrogen.
Synthetic gas is a fuel gas mixture consisting primarily of hydrogen, carbon monoxide, and very often
some carbon dioxide:
The first equation being highly endothermic, consumes tremendous amount of energy. Also carbon
monoxide is the raw material for the second reaction, this has become a cause of concern around the globe as it is
a greenhouse gas and the cost of reformer plant does not suffice for the amount of hydrogen produced.
Researchers at NREL are developing advanced processes to produce hydrogen economically from
sustainable resources. Researchers are now focusing on the following methods of extracting hydrogen:
1. Biological water splitting
2. Fermentation
3. Conversion of biomass and wastes
4. Photo electrochemical water splitting
5. Solar Thermal water splitting
6. Renewable electrolysis
7. Hydrogen dispenser hose reliability
8. Hydrogen production and delivery pathway analysis.
4.2 Production from coal
Hydrogen can be produced from coal through a variety of gasification processes (e.g. fixed bed,
fluidized bed or entrained flow) [2]. In practice, high-temperature entrained flow processes are favored to
maximize carbon conversion to gas, thus avoiding the formation of significant amounts of char, tars and
phenols. A typical reaction for the process I s given in the equation below, in which carbon is converted to
carbon monoxide and hydrogen:
(1) C(s) + H2O + heat ➞ CO + H2
Since this reaction is endothermic, additional heat is required, as with methane reforming. The CO is
further converted to CO2 and H2 through the water-gas shift reaction. Hydrogen production from coal is
commercially mature, but it is more complex than the production of hydrogen from natural gas. The cost of the
resulting hydrogen is also higher. But since coal is plentiful in many parts of the world and will probably be

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DOI: 10.9790/1684-12234450 www.iosrjournals.org 46 | Page
used as an energy source regardless, it is worthwhile to explore the development of clean technologies for its
use.
V. Hydrogen Storage
When it comes to using hydrogen as a source of power to be used in vehicles, it is the storage of
hydrogen that poses one of the bigger challenges. As discussed before, hydrogen, having a lower weight-by-
volume ratio, requires a space considerably more than that required to store the same amount of gasoline under
similar conditions. Using a larger tank for the hydrogen is neither practical nor efficient as far as the design of
the car is concerned, which has led to the development of better alternatives for the storage of hydrogen.
5.1 Liquid hydrogen
Liquefied hydrogen does away with the problem of low density prevalent in gaseous hydrogen. Liquid
hydrogen vehicular storage systems have some of the highest mass fractions and lowest system volumes. This
makes it a strong contender to be used in vehicles. As the hydrogen is in liquid state, it becomes increasingly
easy to store it and to fill the vehicle tanks.
Though the liquefaction process of hydrogen is a considerably costly one, since, it is said to take up
high energies for liquefaction to the order of almost 30% of the hydrogen heating value. Also when it comes to
hydrogen, the factor of dormancy is one of the frequently faced problems. Liquid hydrogen too has this very
drawback. When liquid hydrogen is stored unused for a certain period of time, high level of boil-off losses occur
thus the overall efficiency of the storage system is highly reduced.
But all this said, it can be argued that liquid hydrogen is still the best alternative for vehicular
applications since the various advantages of liquid hydrogen like its safety characteristics, higher density and its
current success record overshadows its few disadvantages like dormancy and production costs.
5.2 Metal hydrides
Metal hydrides are arguably the best way to store hydrogen for portable use. These work on the
principle of dissociation of gaseous hydrogen at a certain temperature. Accordingly the metal hydrides are
widely divided into two types: low dissociation temperature hydrides and high dissociation temperature
hydrides.
Both of these systems have good safety characteristics. But this presents a dilemma when choosing the
type of hydride to be used. The safety characteristics of metal hydrides increase with the increase in the
dissociation temperatures. This is so because the higher the dissociative temperatures are, lesser are the
probability of the hydrogen getting discharged spontaneously in the incident of a crash. Also the low
dissociation temperature metal hydrides have a hydrogen fraction which is too low for vehicular uses and
similarly the high dissociation temperature metal hydrides need a temperature of the order of 300°C which is too
high to be used in cars. Also, there is lot of precedent of metal hydrides being too heavy for vehicular use.
Considering all the aspects, metal hydrides can be used in vehicles only if a right compromise is found
between low and high dissociation temperature hydrides. Though using the exhaust heat of the vehicle for the
discharge of hydrogen from the metal hydrides is a field which has a lot of prospective.
5.3 Carbon adsorption
This method of hydrogen storage draws its advantages and functioning from the adsorbent properties of
carbon. The adhesion present between carbon and hydrogen gas can be used to adsorb hydrogen and thus
increase the volumetric density. Carbon nano fibres possess great potential in these aspects due to its adsorbent
properties and the ease of design associated with carbon fibres.
Although the development of nano fibres for this purpose is at a speculative, it opens wide new
possibilities in optimally designed hydrogen storage systems.
5.4 Compressed Hydrogen Gas
As the name suggests, hydrogen gas can be stored in specially designed tanks more effectively by
pressurising it to a certain pre-determined level. The normally used pressure for this purpose is about 5000 psi.
This remarkably improves the density characteristics of hydrogen for vehicular uses. The commonly used tanks
for this purpose are metal or plastic lined, carbon fibre wound pressure vessels.
The advantage of this method is that the designer does not face the challenge of facilitating a tank of a
large size into the design as the tank volume gets considerably reduced. But the greatest advantage is that of
absence of dormancy issues usually found in liquid hydrogen.
However transportation of compressed hydrogen gas is less effective than that of liquid hydrogen.
Compressed hydrogen gas is supportable by small scale as well as large H2 production facilities. Thus the

4. Hydrogen Powered Vehicles- An Overview
DOI: 10.9790/1684-12234450 www.iosrjournals.org 47 | Page
production of compressed hydrogen can be effectively incorporated in a larger liquid hydrogen production
facility.
The recurring disadvantages of this method are high cost of production and speculative safety characteristics.
VI. Hydrogen Fuel Cell
6.1 Hydrogen Fuel Cell Working
Like a fuel cell, battery also is an electrochemical device. A battery has all of its chemicals stored
inside, and it converts those chemicals into electricity. This means that a battery eventually "goes dead" and you
either throw it away or recharge it.
For a fuel cell chemicals constantly flow into the cell so it never goes dead. As long as there is a flow
of chemicals into the cell, the electricity flows out of the cell. Most fuel cells in use today use hydrogen and
oxygen as the chemicals.
Fuel Cells generate electricity through an electrochemical process in which the energy stored in a fuel
is converted directly into DC electricity. As electrical energy is generated without combusting fuel, fuel cells are
extremely attractive from an environmental stand point. It consists of three components - a cathode, an anode,
and an electrolyte sandwiched between the two. Oxygen from the air flows through the cathode. A fuel gas
containing hydrogen, such as methane, flows past the anode.
Fig. 1
6.2 Principle
An input fuel is catalytically reacted (electrons removed from the fuel elements) in the fuel cell to
create an electric current. Fuel cells consist of an electrolyte material which is sandwiched in between two thin
electrodes (porous anode and cathode). The input fuel passes over the anode (and oxygen over the cathode)
where it catalytically splits into ions and electrons. The electrons go through an external circuit to serve an
electric load while the ions move through the electrolyte toward the oppositely charged electrode. At the
electrode, ions combine to create by-products, primarily water and heat. Depending on the input fuel and
electrolyte, different chemical reactions will occur.
Fig. 2

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6.3 Hydrogen Fuel Cells
Like every other thing in nature, hydrogen fuel cells too have their pros and cons. To decide whether hydrogen
fuel cells can be a dream come true is however ambiguous.
6.3.1 Advantages
1. Hydrogen is readily available as there is no element in the entire universe as abundant as it.
2. Hydrogen is also a great source of energy as the energy content of hydrogen is the highest per unit of
weight of any fuel, and thus, hydrogen fuel cells are considered as a favorable replacement for fossil fuels.
3. The most important feature of hydrogen fuel cells however is the fact that once the hydrogen gas is burnt it
gives out water as a byproduct.
4. Hydrogen fuel cells have a higher efficiency than diesel or gas engines.
Besides being fuel efficient, hydrogen energy is powerful enough to propel spaceships. The gas is also
non-toxic, which makes it a rarity amongst fuel sources. Nuclear energy, coal, and gasoline are all either toxic or
found in hazardous environments. This makes hydrogen ideal for use in a number of ways other fuel sources
can’t compete against. The usage of hydrogen energy will greatly reduce the dependency on foreign oil.
6.3.2 Disadvantages:
As mentioned before, hydrogen is the most abundant element in the universe. However, it is still currently
expensive as it is difficult to generate and store.
1. Hydrogen gas requires a lot of work to free it from other elements.
2. It’s expensive and time-consuming to produce.
3. Though hydrogen energy is renewable and its environmental impacts are minimal, we still need other non-
renewable sources like coal, oil and natural gas to separate it from oxygen.
4. Major obstacle to widespread use of fuel cells is in the storage and distribution of the hydrogen fuel.
5. Hydrogen gas is difficult to contain, and most methods add considerable weight to a vehicle.
6. Because of its volatility, the safety of hydrogen will always be a concern.
7. Hydrogen is highly flammable and thus has the potential risks associated with it.
8. The technology and infrastructure required to support the distribution of hydrogen fuel cells is not fully
developed yet and thus hydrogen fuel cells are considered to be at least decades away from its commercial
use.
VII. Hydrogen Internal Combustion Engines
As the drawbacks of FCV'S are a cause of concern, an alternative technology or method is of
paramount importance to bridge the gap between FCV'S and conventional SI/CI Engines. With over a century of
R&D since its inception the IC engines are most reliable and affordable but still environmentally challenging
propulsive systems. This obstacle can however overcome by usage of an alternative source of fuel-like
Hydrogen which on combustion with oxygen gives water. This is possible because we have the existing
technology of SI/CI engines and need to make further relevant changes in order to put it actual use.
An overview of design considerations for a hydrogen fuelled IC Engine are as follows [4];
1. Abnormal combustion: The suppression of abnormal combustion and the backfire has been a particularly
strenuous obstacle to development of hydrogen engines. Also the design of piston should be sufficiently flat so
as to allow proper mixing of air-hydrogen mixture.
2. Air fuel mixture: Wide range of air-fuel mixtures have been tested for backfire free operations. External
mixture formation by means of a port fuel injection method shows increased efficiency, extended lean operation
and reduce NOx emissions over direct injection method, well the possibility of backfire is almost negligible in
DI compared to PFI.
3. Load control: As we are well aware of hydrogen flammability and its flame speed limits, it permits lean
operation of engines thus the engine efficiency and NOx emissions are responsible load control methods.
4. Hydrogen SI engines: The design and development of hydrogen engines depend on the design of spark
plugs, ignition system, piston and crevice volumes, injectors, compression ratio, hotspots, lubrication and in
cylinder turbulence to name a few.
7.1 Advantages
1. High flammability range
2. High speed burning of flame or turbulence in the cylinder and high octane rating of hydrogen all contributes
the increase in engine efficiency.
3. No greenhouse gases are emitted due to absence of carbon content and NOx emissions are being reduced.

6. Hydrogen Powered Vehicles- An Overview
DOI: 10.9790/1684-12234450 www.iosrjournals.org 49 | Page
7.2 Disadvantages
1. Cost of Hydrogen SI engine is more compared to its gasoline counterpart.
2. The power output at low loads and the reduction of NOx emission in subsequent years.
VIII. Comparison of HFC’s Vs HICE Vs SI/CI Engines
Taking the test results and various parameters into consideration, the graph (1) shows that the highest
efficiency to load ratio is obtained in HFC'S followed by hydrogen ICE, conventional Diesel and Petrol engines
respectively.
Fig. 3
Thus the final comparison is been drafted in the TABLE (1), which clearly shows that hydrogen powered
vehicles are more fuel efficient than conventional engines.
Table 1:
GASOLINE
INTERNAL
COMBUSTION
ENGINE
GASOLINE HYBRID
HYDROGEN
INTERNAL
COMBUSTION
ENGINE
HYDROGEN FUEL
CELL
ENGINE TYPE SPARK-IGNITION
SPARK-IGNITION &
ELECTRIC MOTOR
COMPRESSED
IGNITION (WITH
ELECTRIC MOTOR)
FUEL CELL &
ELECTRIC MOTOR
AVERAGE ENGINE
EFFICIENCY
~30% ~30% ~40% ~55%
MAX ENGINE
EFFICIENCY
32.5% 32.5% ~40% ~65%
TRANSMISSION
TYPE
STANDARD
CONTINUOUSLY
VARIABLE
TRANSMISSION/
HYBRID
CONTINUOUSLY
VARIABLE
TRANSMISSION/
LIKELY
HYBRID
CONTINUOUSLY
VARIABLE
TRANSMISSION /
LIKELY
HYBRID
TRANSMISSION
EFFICIENCY
~40% ~60% ~60% ~60%
FUEL ECONOMY
(MILES PER
GALLON
EQUIVALENT.)
21 31 41 51
IX. Conclusion
Thus we can see that hydrogen powered vehicles can be significant alternative for the future power
needs and it still has a great scope for research in many areas. Though HFC’S wont venture into mass
production so soon, the scope of Hydrogen ICE looks promising in the immediate future bridging the
technological gap between HFC'S and conventional Petrol/Diesel engines.
This paper instills the future scope and the rising demand of an alternative fuel for conventional
engines and with hydrogen as the fuel; it might just be the one.

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step in wrong direction? Stanford global climate and energy project working paper.
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Petroleum and Gas,V.4n.3,P.119-127,(2010),ISSN 1982-0593.
[3]. Brian D. James Overview of Hydrogen Storage Technologies, Argonne National Laboratory
[4]. VVN Bhaskar* et.al/International Journal of Innovative Technology and Research, Vol. 1, Issue 1, Dec-
Jan(2013),046-053